A supersized 3 and regular-sized 0 was the last one I remember. I use both; they are meant to b used together. It would make more sense to supersize the 0 since you're supposed to saturate your hair with it and my hair sucks it up.
I also use 1 & 2 every other time when I color, but those are not readily available to the general public, although it can be gotten. The effect is dramatic my first color after getting a perm as far as how healthy my hair feels and appears.
The others have silicones, so I don't use those. However 9 I think is new and I've read that it is Curly Girl safe, so I may have to look into that one.